Objective:

(1) Develop novel methods to measure model parameters (C0 and Y0) for 20 representative sources that emit 27 SVOCs, and use the resulting data at five temperatures (from 25°C to 85°C) to establish the nature of the equilibrium relationship; (2) Develop novel methods to determine surface/air partition coefficients (K) for eight detected SVOCs and six interior surfaces including airborne particles (Kp) and dust (Kdust), and compare results to available correlations for Ks, Kp, and Kdust; (3) Conduct single-source chamber experiments to characterize emissions of target SVOCs from the 20 representative sources at five temperatures (from 25°C to 85°C); (4) Validate the single-source model using results from the chamber experiments for the 20 representative sources and the single-phase model using data collected from the literature; and (5) Evaluate assumptions on which the rapid single-source and single-phase methods are based and characterize the uncertainty inherent in model predictions, especially for the low volatility SVOCs.

Approach:

Modern indoor environments contain a vast array of products, many of which emit toxic semi-volatile organic compounds (SVOCs). There is an urgent need to estimate exposure to SVOCs, but the vast number of SVOC/product combinations poses a serious challenge. To solve this problem, we propose two distinct rapid methods to estimate exposure, both based on the same set of assumptions. The first is the "single-source" approach, in which we characterize a specific indoor product and then estimate exposure. The second is the "single-phase" approach, in which we characterize a particular indoor phase, for example, the indoor air, and then estimate exposure. Collectively, the single-source and single-phase approaches represent a very powerful way to solve the problem. The single-phase approach can be applied to get broad, population-wide, information about exposure to SVOCs in general. The single-source approach can rapidly characterize specific SVOC/product combinations, and estimate their contributions to exposure. This information can then be used to either remove specific products from the market, or make substitutions, introducing alternate low toxicity SVOCs that impart similarly desirable product performance at equivalent cost.

Expected Results:

Include: (a) A validated single-source model that can be used to make rapid estimates of exposure to SVOCs released from specific products used indoors; and (b) A validated single-phase model that can be used to make rapid estimated of exposure to a wide range of SVOCs, based only on the average concentration of SVOCs found in indoor air. Expected benefits are significant. When combined with the rapid estimates of toxicity being developed in ToxCast™, our rapid estimates of exposure will allow risk-based prioritization of a wide range of SVOCs, representing a powerful screening tool to rapidly estimate, prioritize and reduce, public health risks associated with SVOCs indoors.

Supplemental Keywords:

Progress and Final Reports:

The perspectives, information and conclusions conveyed in research project abstracts, progress reports, final reports, journal abstracts and journal publications convey the viewpoints of the principal investigator and may not represent the views and policies of ORD and EPA. Conclusions drawn by the principal investigators have not been reviewed by the Agency.